1. Field of the Invention
The present invention relates to a headlamp for an automobile, a motorcycle or a motor-driven bicycle (hereinafter typically referred to as "a vehicular headlamp", when applicable), and more particularly to a projection type vehicular headlamp in which a light beam emitted from a light source and reflected by a reflector is irradiated through a projection lens.
There has been known vehicular headlamps of the projection type as disclosed, for example, in U.S. Pat. No. 4,631,642. The headlamp of this type is so designed that, as shown in FIG. 1, the light beam emitted from a light source, namely, a light bulb 2, is reflected by a reflector 3, and the light beam thus reflected is irradiated through a projection lens 4. The reflector 3 accommodating the light bulb 2, and a lens holder 5 holding the projection lens 4 are unitary engaged with each other thereby forming a projection unit 1.
Recently, the headlamp thus designed has been extensively employed in the art, because, when compared with a headlamp using a parabolic reflector, it is compact and large in the quantity of light, and provides a desired clear cut-off line.
However, the employment of the projection type headlamp for a motorcycle suffers from the following difficulties: Since the projection type headlamp is large in light intensity, as shown in FIG. 2 irradiation area A and the non-irradiation area B formed in front of the motor cycle are excessively different in brightness, and the visibility is low at the border region C (shaded in FIG. 2) between these two areas A and B.